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Side by Side Diff: third_party/chrome/base/scoped_ptr.h

Issue 624713003: Keep only base/extractor.[cc|h]. (Closed) Base URL: https://chromium.googlesource.com/external/omaha.git@master
Patch Set: Created 6 years, 2 months ago
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1 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 // Scopers help you manage ownership of a pointer, helping you easily manage the
6 // a pointer within a scope, and automatically destroying the pointer at the
7 // end of a scope. There are two main classes you will use, which coorespond
8 // to the operators new/delete and new[]/delete[].
9 //
10 // Example usage (scoped_ptr):
11 // {
12 // scoped_ptr<Foo> foo(new Foo("wee"));
13 // } // foo goes out of scope, releasing the pointer with it.
14 //
15 // {
16 // scoped_ptr<Foo> foo; // No pointer managed.
17 // foo.reset(new Foo("wee")); // Now a pointer is managed.
18 // foo.reset(new Foo("wee2")); // Foo("wee") was destroyed.
19 // foo.reset(new Foo("wee3")); // Foo("wee2") was destroyed.
20 // foo->Method(); // Foo::Method() called.
21 // foo.get()->Method(); // Foo::Method() called.
22 // SomeFunc(foo.Release()); // SomeFunc takes owernship, foo no longer
23 // // manages a pointer.
24 // foo.reset(new Foo("wee4")); // foo manages a pointer again.
25 // foo.reset(); // Foo("wee4") destroyed, foo no longer
26 // // manages a pointer.
27 // } // foo wasn't managing a pointer, so nothing was destroyed.
28 //
29 // Example usage (scoped_array):
30 // {
31 // scoped_array<Foo> foo(new Foo[100]);
32 // foo.get()->Method(); // Foo::Method on the 0th element.
33 // foo[10].Method(); // Foo::Method on the 10th element.
34 // }
35
36 #ifndef BASE_SCOPED_PTR_H_
37 #define BASE_SCOPED_PTR_H_
38
39 // This is an implementation designed to match the anticipated future TR2
40 // implementation of the scoped_ptr class, and its closely-related brethren,
41 // scoped_array, scoped_ptr_malloc.
42
43 #include <assert.h>
44 #include <stdlib.h>
45 #include <cstddef>
46
47 // A scoped_ptr<T> is like a T*, except that the destructor of scoped_ptr<T>
48 // automatically deletes the pointer it holds (if any).
49 // That is, scoped_ptr<T> owns the T object that it points to.
50 // Like a T*, a scoped_ptr<T> may hold either NULL or a pointer to a T object.
51 // Also like T*, scoped_ptr<T> is thread-compatible, and once you
52 // dereference it, you get the threadsafety guarantees of T.
53 //
54 // The size of a scoped_ptr is small:
55 // sizeof(scoped_ptr<C>) == sizeof(C*)
56 template <class C>
57 class scoped_ptr {
58 public:
59
60 // The element type
61 typedef C element_type;
62
63 // Constructor. Defaults to intializing with NULL.
64 // There is no way to create an uninitialized scoped_ptr.
65 // The input parameter must be allocated with new.
66 explicit scoped_ptr(C* p = NULL) : ptr_(p) { }
67
68 // Destructor. If there is a C object, delete it.
69 // We don't need to test ptr_ == NULL because C++ does that for us.
70 ~scoped_ptr() {
71 enum { type_must_be_complete = sizeof(C) };
72 delete ptr_;
73 }
74
75 // Reset. Deletes the current owned object, if any.
76 // Then takes ownership of a new object, if given.
77 // this->reset(this->get()) works.
78 void reset(C* p = NULL) {
79 if (p != ptr_) {
80 enum { type_must_be_complete = sizeof(C) };
81 delete ptr_;
82 ptr_ = p;
83 }
84 }
85
86 // Accessors to get the owned object.
87 // operator* and operator-> will assert() if there is no current object.
88 C& operator*() const {
89 assert(ptr_ != NULL);
90 return *ptr_;
91 }
92 C* operator->() const {
93 assert(ptr_ != NULL);
94 return ptr_;
95 }
96 C* get() const { return ptr_; }
97
98 // Comparison operators.
99 // These return whether two scoped_ptr refer to the same object, not just to
100 // two different but equal objects.
101 bool operator==(C* p) const { return ptr_ == p; }
102 bool operator!=(C* p) const { return ptr_ != p; }
103
104 // Swap two scoped pointers.
105 void swap(scoped_ptr& p2) {
106 C* tmp = ptr_;
107 ptr_ = p2.ptr_;
108 p2.ptr_ = tmp;
109 }
110
111 // Release a pointer.
112 // The return value is the current pointer held by this object.
113 // If this object holds a NULL pointer, the return value is NULL.
114 // After this operation, this object will hold a NULL pointer,
115 // and will not own the object any more.
116 C* release() {
117 C* retVal = ptr_;
118 ptr_ = NULL;
119 return retVal;
120 }
121
122 private:
123 C* ptr_;
124
125 // Forbid comparison of scoped_ptr types. If C2 != C, it totally doesn't
126 // make sense, and if C2 == C, it still doesn't make sense because you should
127 // never have the same object owned by two different scoped_ptrs.
128 template <class C2> bool operator==(scoped_ptr<C2> const& p2) const;
129 template <class C2> bool operator!=(scoped_ptr<C2> const& p2) const;
130
131 // Disallow evil constructors
132 scoped_ptr(const scoped_ptr&);
133 void operator=(const scoped_ptr&);
134 };
135
136 // Free functions
137 template <class C>
138 void swap(scoped_ptr<C>& p1, scoped_ptr<C>& p2) {
139 p1.swap(p2);
140 }
141
142 template <class C>
143 bool operator==(C* p1, const scoped_ptr<C>& p2) {
144 return p1 == p2.get();
145 }
146
147 template <class C>
148 bool operator!=(C* p1, const scoped_ptr<C>& p2) {
149 return p1 != p2.get();
150 }
151
152 // scoped_array<C> is like scoped_ptr<C>, except that the caller must allocate
153 // with new [] and the destructor deletes objects with delete [].
154 //
155 // As with scoped_ptr<C>, a scoped_array<C> either points to an object
156 // or is NULL. A scoped_array<C> owns the object that it points to.
157 // scoped_array<T> is thread-compatible, and once you index into it,
158 // the returned objects have only the threadsafety guarantees of T.
159 //
160 // Size: sizeof(scoped_array<C>) == sizeof(C*)
161 template <class C>
162 class scoped_array {
163 public:
164
165 // The element type
166 typedef C element_type;
167
168 // Constructor. Defaults to intializing with NULL.
169 // There is no way to create an uninitialized scoped_array.
170 // The input parameter must be allocated with new [].
171 explicit scoped_array(C* p = NULL) : array_(p) { }
172
173 // Destructor. If there is a C object, delete it.
174 // We don't need to test ptr_ == NULL because C++ does that for us.
175 ~scoped_array() {
176 enum { type_must_be_complete = sizeof(C) };
177 delete[] array_;
178 }
179
180 // Reset. Deletes the current owned object, if any.
181 // Then takes ownership of a new object, if given.
182 // this->reset(this->get()) works.
183 void reset(C* p = NULL) {
184 if (p != array_) {
185 enum { type_must_be_complete = sizeof(C) };
186 delete[] array_;
187 array_ = p;
188 }
189 }
190
191 // Get one element of the current object.
192 // Will assert() if there is no current object, or index i is negative.
193 C& operator[](std::ptrdiff_t i) const {
194 assert(i >= 0);
195 assert(array_ != NULL);
196 return array_[i];
197 }
198
199 // Get a pointer to the zeroth element of the current object.
200 // If there is no current object, return NULL.
201 C* get() const {
202 return array_;
203 }
204
205 // Comparison operators.
206 // These return whether two scoped_array refer to the same object, not just to
207 // two different but equal objects.
208 bool operator==(C* p) const { return array_ == p; }
209 bool operator!=(C* p) const { return array_ != p; }
210
211 // Swap two scoped arrays.
212 void swap(scoped_array& p2) {
213 C* tmp = array_;
214 array_ = p2.array_;
215 p2.array_ = tmp;
216 }
217
218 // Release an array.
219 // The return value is the current pointer held by this object.
220 // If this object holds a NULL pointer, the return value is NULL.
221 // After this operation, this object will hold a NULL pointer,
222 // and will not own the object any more.
223 C* release() {
224 C* retVal = array_;
225 array_ = NULL;
226 return retVal;
227 }
228
229 private:
230 C* array_;
231
232 // Forbid comparison of different scoped_array types.
233 template <class C2> bool operator==(scoped_array<C2> const& p2) const;
234 template <class C2> bool operator!=(scoped_array<C2> const& p2) const;
235
236 // Disallow evil constructors
237 scoped_array(const scoped_array&);
238 void operator=(const scoped_array&);
239 };
240
241 // Free functions
242 template <class C>
243 void swap(scoped_array<C>& p1, scoped_array<C>& p2) {
244 p1.swap(p2);
245 }
246
247 template <class C>
248 bool operator==(C* p1, const scoped_array<C>& p2) {
249 return p1 == p2.get();
250 }
251
252 template <class C>
253 bool operator!=(C* p1, const scoped_array<C>& p2) {
254 return p1 != p2.get();
255 }
256
257 // This class wraps the c library function free() in a class that can be
258 // passed as a template argument to scoped_ptr_malloc below.
259 class ScopedPtrMallocFree {
260 public:
261 inline void operator()(void* x) const {
262 free(x);
263 }
264 };
265
266 // scoped_ptr_malloc<> is similar to scoped_ptr<>, but it accepts a
267 // second template argument, the functor used to free the object.
268
269 template<class C, class FreeProc = ScopedPtrMallocFree>
270 class scoped_ptr_malloc {
271 public:
272
273 // The element type
274 typedef C element_type;
275
276 // Constructor. Defaults to intializing with NULL.
277 // There is no way to create an uninitialized scoped_ptr.
278 // The input parameter must be allocated with an allocator that matches the
279 // Free functor. For the default Free functor, this is malloc, calloc, or
280 // realloc.
281 explicit scoped_ptr_malloc(C* p = NULL): ptr_(p) {}
282
283 // Destructor. If there is a C object, call the Free functor.
284 ~scoped_ptr_malloc() {
285 free_(ptr_);
286 }
287
288 // Reset. Calls the Free functor on the current owned object, if any.
289 // Then takes ownership of a new object, if given.
290 // this->reset(this->get()) works.
291 void reset(C* p = NULL) {
292 if (ptr_ != p) {
293 free_(ptr_);
294 ptr_ = p;
295 }
296 }
297
298 // Get the current object.
299 // operator* and operator-> will cause an assert() failure if there is
300 // no current object.
301 C& operator*() const {
302 assert(ptr_ != NULL);
303 return *ptr_;
304 }
305
306 C* operator->() const {
307 assert(ptr_ != NULL);
308 return ptr_;
309 }
310
311 C* get() const {
312 return ptr_;
313 }
314
315 // Comparison operators.
316 // These return whether a scoped_ptr_malloc and a plain pointer refer
317 // to the same object, not just to two different but equal objects.
318 // For compatibility wwith the boost-derived implementation, these
319 // take non-const arguments.
320 bool operator==(C* p) const {
321 return ptr_ == p;
322 }
323
324 bool operator!=(C* p) const {
325 return ptr_ != p;
326 }
327
328 // Swap two scoped pointers.
329 void swap(scoped_ptr_malloc & b) {
330 C* tmp = b.ptr_;
331 b.ptr_ = ptr_;
332 ptr_ = tmp;
333 }
334
335 // Release a pointer.
336 // The return value is the current pointer held by this object.
337 // If this object holds a NULL pointer, the return value is NULL.
338 // After this operation, this object will hold a NULL pointer,
339 // and will not own the object any more.
340 C* release() {
341 C* tmp = ptr_;
342 ptr_ = NULL;
343 return tmp;
344 }
345
346 private:
347 C* ptr_;
348
349 // no reason to use these: each scoped_ptr_malloc should have its own object
350 template <class C2, class GP>
351 bool operator==(scoped_ptr_malloc<C2, GP> const& p) const;
352 template <class C2, class GP>
353 bool operator!=(scoped_ptr_malloc<C2, GP> const& p) const;
354
355 static FreeProc const free_;
356
357 // Disallow evil constructors
358 scoped_ptr_malloc(const scoped_ptr_malloc&);
359 void operator=(const scoped_ptr_malloc&);
360 };
361
362 template<class C, class FP>
363 FP const scoped_ptr_malloc<C, FP>::free_ = FP();
364
365 template<class C, class FP> inline
366 void swap(scoped_ptr_malloc<C, FP>& a, scoped_ptr_malloc<C, FP>& b) {
367 a.swap(b);
368 }
369
370 template<class C, class FP> inline
371 bool operator==(C* p, const scoped_ptr_malloc<C, FP>& b) {
372 return p == b.get();
373 }
374
375 template<class C, class FP> inline
376 bool operator!=(C* p, const scoped_ptr_malloc<C, FP>& b) {
377 return p != b.get();
378 }
379
380 #endif // BASE_SCOPED_PTR_H_
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